Rhodamine coloring matters and process for preparing the same



Patented Feb. 18, 1936 PATENT OFFICE RHODAMINE COLORING MATTERS AND PROCESS FOR PREPARING THE SAIVIE Max Wyler, Blackley, Manchester, England, assignor to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application June 28, 1934, Serial No. 732,928. In Great Britain June 30, 1933 9 Claims.

This invention relates to new coloring matters of the rhodamine series.

It is an object of this invention to produce new organic compounds of the rhodamine series useful as lake coloring matters. It is a further object of this invention to produce compounds of the rhodamine series which may be rendered soluble by sulfonation, thereby adapting them for use as dyestuffs for textile material. Other and 10 further important objects of this invention, will appear as the description proceeds.

I accomplish the objects of my invention by synthesizing new organic compounds of the rhodamine series from the usual alkyl-amino-phenols employed for this purpose and naphthalene-2,3- dicarboxylic acid or its anhydride. The novel compounds thus produced are characterized by possessing in their structure the fundamental nucleus C O O- 5 wherein the N atoms are substituted by the usual alkyl radicals or hydrogen, or inorganic acid radicals, and the O atom of the CO0 group is substituted by hydrogen, an alkali-metal, or an alkyl radical, or it forms an inner ring with the,adja-- cent Catom. As 'in the case of the orinary rhodamine compounds, my novel compounds may be isolated as a salt, such as the hydrochloride or sulfate, or they may be esterified. They may also be sulfonated to impart to them water-solubility, as more fully described below.

My process of synthesizing these novel compounds is analogous to those used in the art for syntherizing rhodamine colors in general, ex- 50 cept that instead of phthalic acid or anhydride I use naphthalene-2,3-dicarboxylic acid or its anhydride. In other words, my process consists generally of reacting one mole or an excess of one mole of naphthalene-2,3dicarboxylic acid with two moles of an alkyl amino-phenol, preferably in the presence of a metal halide condensing agent.

Heretofore, neither naphthalene-2,3-dicarboxylic acid nor its anhydride have been used for the manufacture of rhodamine coloring matters 10 or dyestuffs. I have now found that they may replace phthalic acid or anyhdride in the manu-- facture of rhodamines by methods known per se from N -alkylor NN-dialkyl-aminophenols. The

resulting new unsulphonated rhodamine dyestuffs are similar in shade to the corresponding known rhodamines from phthalic acid, but are insufliciently soluble in water to be valuable in textile dyeing, although they can be used as lake coloring matters. I have found, however, that they can be sulfonated with ease by known methods and that the sulfonated products are acid dyes which, for instance, dye wool in brilliant shades of good to very good fastness.

The following examples in which parts are 25 by weight illustrate but do not limit the invention.

Example I 21.6 parts of naphthalene-2,3-dicarboxylic acid, 30

16.5 parts of diethyl-m-aminophenol, and 10.0 parts of fused zinc chloride are mixed and heated gradually to 200 C. and kept at this till the melt becomes nearly solid. The melt is allowed to cool, ground and extracted with warm water to 35 remove zinc salts. The resulting insoluble matter is then stirred at C. with 100 parts of 10% aqueous caustic soda, filtered, washed and recrystallized from toluene. The resulting. base is in beautiful orange-colored needles. It can be 40 converted to sulphate by dissolving in boiling dilute sulphuric acid and then adding a little sodium chloride to convert the resulting gelatinous product into crystals. It dyes tanninmordanted cotton in the same shade as rhodamine B (Colour Index No. 749), but it is not sufficiently soluble to find practical application in this way.

Sulfonation is effected by dissolving the melt Erample II By replacing in Example I, 16.5 parts of dicompound of the general COOH 1. A rhodamine formula ethyl-m-aminophenol by 13.7 parts of mono-' ethyl-m-aminophenol, but otherwise proceeding in the same manner a more insoluble product is obtained, the sulphate of the base being very insoluble even after esterification. The base is sulfonated as in the previous example and the resulting product dyes wool a bright red-orange shade of very good fastness.

Example III *Instead of 1615 parts of diethyl-m-amino phenol in Example I, 15.1 parts of ethylamino-pcresol are taken. After the melt has been washed free from zinc chloride and the product decomposed with dilute caustic soda solution and dried, the base is esterified in-the following way: 10 parts of base are dissolved in 40 parts of sulphuric acid, 300 parts of ethanol are added and heated under reflux at 100 C. for '12 hours.

" The reaction product is poured into 500parts 01! water, filtered and dissolved in750 parts of boiling water, and the solution left to crystallize. The new rhodamine separates in lustrous green crystals.

brighter than Rhodamine 'GGBS. It is insuificiently soluble to find practical application per se. However, by sulfonating the zinc free melt in exactly the same manner as described in Example I a color is obtained which dyes wool fast red.

It will be understood that many variations and modifications are possible in my preferred mode of procedure, without departing from the spirit of this invention. In general, since the reaction runs along analogous lines with the ordinary rhodamine synthesis, i t,-will be understood that all the modifications, improvements and variations. practiced in the synthesis of knownrhodaminecolorsmay be app ied to the yn hesis and.

use of my new colors above described, Without departing from the essence of this invention.

l'n the claims below, where new compounds, products; or dyestufis are claimed, it will be understood that I intend to cover the same not only in substance, but also in whateverstate they exist when applied .to material, dyed, printed or pigmented therewith.

I claim:

It dyes and prints tannin-mordanted' cotton in shades very similar to but slightly wherein R1 stands for .a lower alkyl radical, while R2 stands for hydrogen or a lower alkyl radical, X stands for the radical of a highly ionizable inorganic acid, and the phenyl nuclei .to which the N atoms are attached may carry further simple monovalent nuclear substituents of the type .generally employed in the aryl nuclei of rhodamine dyestufis.

2. A dyestufi for wool comprising the sulfonic acid of a rhodamine compound obtainable by subjecting naphthalene-2,3-dicarboxylic acid or its anhydride and a meta-alkylamino-phenol to rhodamine synthesis.

"3. A dyestufi for W001 comprising the sulfonic acid of a rhodamine compound obtainable by fusing naphthalene-2,3- dicarboxylic acid with a meta-alkylamino-phenol in the presence of zinc chloride.

4. A process for producing a coloring compound, which comprises subjecting arcompound selected from the group consisting of naphthalene-2;3-dicarboxylic acid and its anhydride and a meta-alkylamino-phenol to rhodamine synthesis, and sulfonating the reaction product.

5. A process for producing a coloring compound, which comprises fusing naphthalene- 2,3-dicarboxylic acid with a meta-alkylaminophenol the presence of zinc chloride, and recovering the water insoluble organic compound.

6. A process for producing a coloring compound, which comprises fusing naphthalene- 2,3-dicarboxylic acid with a meta-alkylaminophenol in the presence ,of zinc chloride, and subjecting the reaction-product to sulfonation.

7. A dyestuff for W001 comprising the sulfonic MAXWYLER. 

